Quarkonium Physics

Monday 3 Jun 2013, 14:00 → 16:00 Europe/Zurich

4/3-006 - TH Conference Room (CERN)

Urs Wiedemann (CERN), Yiota Foka (GSI - Helmholtzzentrum fur Schwerionenforschung GmbH (DE))

1 Thermal width and quarkonium dissociation in an EFT framework

We discuss quarkonium dissociation in a weakly coupled plasma over a wide range of temperatures using the language of thermal and non-relativistic effective field theories. Two major decay mechanisms are found responsible for the quarkonium width: dissociation by inelastic parton scattering (Landau damping) and gluodissociation (singlet-to-octet break up). We calculate the corresponding thermal decay widths and cross sections. Finally, we relate the EFT results to previous findings.

Speaker: Antonio Vairo

Slides HIF13.pdf

2 Heavy quarkonium moving throught a quark gluon plasma

The dissociation of heavy quarkonium seen in heavy-ion collisions is a phenomena that allows to extract information of the produced thermal medium. In recent years a program to study heavy quarkonium with the use of non-relativistic effective field theories has been started, this allows to make the computations in a more systematic way by defining a more suitable power counting and making it more difficult to miss necessary resummations. However, most of the studies using effective field theories have assumed perfect thermal equilibrium and a bound state comoving with the medium, which is far for the experimentally realize situation. In this talk I will review the results of effective field theories for heavy quarkonium in a thermal medium and I will discuss how these results are affected when the bound state has a finite momentum with respect to the thermal medium.

Speaker: Miguel Escobedo

Slides hif_escobedo.pdf

3 ALICE results on quarkonium hadroproduction

In heavy-ion collisions at the LHC, the ALICE experiment is studying nuclear matter at very high energy density where the formation of a Quark Gluon Plasma (QGP) is expected. Quarkonium production is an important probe to characterize the properties of the QGP as it gives access to the early stages of the collision. High precision data in pp collisions provide the baseline of the Pb-Pb measurements and p-Pb collisions serve to quantify the amount of initial and/or final state effects related to cold nuclear matter that are largely unknown at the LHC energy. Since 2010, the LHC provided Pb-Pb collisions at √s = 2.76 TeV per nucleon pair, pp collisions at various energy and earlier this year p-Pb collisions at √s = 5.02 TeV per nucleon pair. In ALICE, quarkonia can be reconstructed down to zero transverse momentum in the dielectron channel at midrapidity and in the dimuon channel at forward rapidity. The measurements of the J/psi (mid- and forward rapidity), Upsilon and psi’ (forward rapidity) in Pb-Pb collisions will be presented and compared to their productions in pp collisions at the same energy. In p-Pb collisions, I will report on the first results on J/psi production at forward rapidity.

Speakers: Cynthia Hadjidakis, Cynthia Hadjidakis (Universite de Paris-Sud 11 (FR))

Slides HIFCern2013-Cynthia.pdf

4 Quarkonia studies in heavy-ion collisions with CMS

The Compact Muon Solenoid (CMS) is fully equipped to measure quarkonia in the di-muon decay channel in the high multiplicity environment of nucleus-nucleus collisions. Quarkonia are especially relevant for studying the quark-gluon plasma since they are produced at early times and propagate through the medium, mapping its evolution. CMS has measured the nuclear modification factors of non-prompt J/psi (from b-hadron decays), prompt J/psi, inclusive psi(2S), and the first three Y states in PbPb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV. A suppression of non-prompt J/psi, which is sensitive to the in-medium b-quark energy loss, has been measured at relatively high p_T (6.5 < p_T < 30 GeV/c) in PbPb collisions, compared to the yield in pp collisions scaled by the number of inelastic nucleon-nucleon collisions. For prompt J/psi in the same kinematic range, a strong, centrality-dependent suppression is observed. Such strong suppression at high p_T has previously not been observed at RHIC. At midrapidity and high p_T, psi(2S) show an even stronger suppression than J/psi. Furthermore, CMS has measured the suppression of the three Y states, separately, down to p_T = 0. A clear ordering of the suppression with binding energy is observed, as expected from sequential melting.

Speaker: Jo Mihee

Slides 3June2013_MiheeJo_HIF.pdf